On Mon, 9 Jan 2006 21:23:51 +0100, Enrico C wrote in
Post by Enrico CPost by Pipponaturalmento per ottenere risultati osservabili occorre forzare un po' la
mano,
Scusa, ma in pratica stai dicendo che senza "forzare la mano", cioè
nell'uso normale, non si ottengono "risultati osservabili"... ovvero
che l'effetto è trascurabile...
Ho provato a cercare su Pubmed studi su eventuali "danni" provocati
dal microonde agli elementi nutritivi del latte (proteine, vitamine,
grassi, ecc...)
Alcuni studi dicono che riscaldare *troppo* il latte (alte
temperature, tempi prolungati) può, in alcuni casi, impoverirlo
nutrizionalmente o addirittura portare alla creazione di sostanze
nocive, ma i "danni", quando ci sono, sono comunque paragonabili sia
quando si usa il microonde sia quando si usano metodi convenzionali
(il metodo di paragone usato di solito negli esperimenti è il
bagnomaria in contenitore con acqua calda).
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=7911811&query_hl=23&itool=pubmed_docsum
J Am Coll Nutr 1994 Apr;13(2):209-10
D-aspartate and D-glutamate in microwaved versus conventionally
heated milk.
Petrucelli L, Fisher GH
Department of Chemistry, Barry University, Miami Shores, Florida
33161.
OBJECTIVE: It has been reported that microwave heating of infant
formulae can isomerize and racemize amino acids in the milk proteins,
causing toxicity or affecting the nutritional value of the milk
formulae. Therefore, we investigated whether microwave heating vs
conventional heating would produce any D- enantiomers of aspartic
acid (Asp) and glutamic acid (Glu) in milk. METHODS: Whole and skim
milk samples were heated for 10 minutes in either a microwave oven at
medium power or on a hot water bath at 80 degrees C. D-Asp and D-Glu
were determined by high performance liquid chromatography. RESULTS:
Unheated (control) samples were found to contain 0.40-0.45% D-Asp and
D-Glu, inherent from the original pasteurizing process. Both
conventional heating and microwave heating induce < 0.25% more
racemization when compared to the control samples. CONCLUSION: Within
experimental error, there is no significant difference in the levels
of these D-amino acids between the conventionally heated and
microwave heated milks, thus having no significant effect on the
nutritional value of the milk proteins.
PMID: 7911811, UI: 94275028
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=8889628&query_hl=26&itool=pubmed_docsum
1: Int J Food Sci Nutr. 1996 Sep;47(5):427-36. Related Articles,
Links
The effect of microwave heating on vitamins B1 and E, and linoleic
and linolenic acids, and immunoglobulins in human milk.
Ovesen L, Jakobsen J, Leth T, Reinholdt J.
Institute of Food Chemistry and Nutrition, National Food Agency,
Copenhagen, Denmark.
Breast milk was treated with (1) conventional heating (in water
bath) vs microwave heating; (2) microwave heating at two power levels
(30% and 100%); (3) increasing final temperatures; and (4) microwave
thawing vs refrigerator thawing and examined for changes in specific
immunoglobulins to a pool of E. coli and poliovirus type 1 antigens,
vitamins E and B1, and the polyunsaturated fatty acids linoleic and
linolenic acid. Immunoglobulin activities were stable until final milk
temperatures of around 60-65 degrees C were reached, and total
inactivation occurred at 77 degrees C. Heating even to high final
temperatures did not change contents of vitamins and polyunsaturated
fatty acids. No differences in immunoglobulins and nutrients were
demonstrated between microwave heating and conventional heating, and
between power levels or thawing methods. The study shows that
microwave heating of human milk can be performed without significant
losses of examined immunoglobulins and nutrients, provided that final
temperatures are below 60 degrees C.
PMID: 8889628 [PubMed - indexed for MEDLINE]
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9891762&query_hl=23&itool=pubmed_docsum
: Amino Acids. 1998;15(4):385-8.
Free amino acid concentrations in milk: effects of microwave
versus conventional heating.
Vasson MP, Farges MC, Sarret A, Cynober L.
Biochemistry, Molecular Biology and Nutrition Laboratory, EA 1742,
Pharmacy School, CRNH, Clermont-Ferrand, France.
M-***@u-clermontl.fr
Microwave effects on free amino acid concentrations in milk versus
a water bath heating were investigated in view of their importance for
infant growth. Concentrations of few amino acids, such as aspartate,
serine or lysine, are unchanged whatever the way and the temperature
of heating. In contrast, tryptophan concentrations decreased similarly
whatever the way of heating (110 +/- 3 mumol/l before heating vs 84
+/- 4 mumol/l after 30 degrees C microwave heating, p < 0.05). On the
contrary, concentrations of glutamate and glycine increased more after
water bath heating at 90 degrees C (325 +/- 4 and 101 +/- 1 mumol/1,
respectively) than after microwave heating (312 +/- 4 and 95 +/- 1
mumol/l, respectively, p < 0.05) suggesting milk proteolysis.
Moreover, the accumulation of ammonia observed at 90 degrees C with
the water bath together with increase Glu levels might reflect a
degradation of glutamine. An ornithine enrichment, more evident with
microwave heating, was shown and could be of interest as it is a
polyamine precursor. Also, considering few variations of free amino
acid concentrations and the time saved, microwave heating appears to
be an appropriate method to heat milk.
PMID: 9891762 [PubMed - indexed for MEDLINE]
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11929283&query_hl=26&itool=pubmed_docsum
1: J Agric Food Chem. 2002 Apr 10;50(8):2274-7.
Mineral balance in milk heated using microwave energy.
de la Fuente MA, Olano A, Juarez M.
Instituto del Frio (CSIC), Ciudad Universitaria s/n, 28040 Madrid,
Spain. ***@if.csic.es
Milk heated to 75 and 85 degrees C in a water bath or in a
microwave oven was assayed for changes in salt partitioning after
cooling to room temperature. To properly to assess differences and
draw valid comparisons, the two heating methods used in the experiment
were applied to samples for identical exposure times, and the samples
were heated to attain the same final temperatures. Although the
soluble Ca and P(i) contents were lower in the heated milk samples, no
significant differences in salt partitioning were found between
microwave and conventional heating. Ionic calcium levels in the milk
samples pasteurized using microwave energy were very close to the
levels in the samples heated in a conventional water bath
(approximately 90% of the level in the untreated milk samples). The
microwave heating-induced changes were completely reversed after
storage at 20 degrees C for 24 h. The coagulation properties of the
heated milk samples were also examined, and the coagulation time was
longer and the curd formation rate slower in the microwave-heated milk
than in the raw milk. Still, the experimental results demonstrated
that microwave heating was no more detrimental to the milk than
conventional heating and could thus be used for pasteurization
purposes.
PMID: 11929283 [PubMed - indexed for MEDLINE]
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11403146&query_hl=29&itool=pubmed_docsum
1: J Food Prot. 2001 Jun;64(6):890-4.
Vitamin B1 and B6 retention in milk after continuous-flow
microwave and conventional heating at high temperatures.
Sierra I, Vidal-Valverde C.
Instituto de Fermentaciones Industriales (CSIC), Madrid, Spain.
The effect of continuous-flow microwave treatment at high
temperatures on the retention of vitamins B1 and B6 in raw milk with
different fat content was evaluated. Results were compared with those
obtained using a conventional system (tubular heat exchanger) with the
same heating and cooling phases. Heat treatment of whole (3.4% fat)
and skim (0.5% fat) milk at 90 degrees C produced no losses of vitamin
B1 or vitamin B6 (pyridoxamine and pyridoxal). However, at 110 and 120
degrees C, while vitamin B1 content of milk remained constant,
pyridoxamine increased (4 to 5% and 9 to 11%, respectively) and
pyridoxal decreased (5 to 6% and 9 to 12%, respectively). Under the
assayed conditions, no differences were observed between the content
of these vitamins in conventionally and continuous-flow
microwave-treated milk.
PMID: 11403146 [PubMed - indexed for MEDLINE]
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=1518698&query_hl=29&itool=pubmed_docsum
1: Pediatrics. 1992 Sep;90(3):412-5.
Microwave heating of infant formula: a dilemma resolved.
Sigman-Grant M, Bush G, Anantheswaran R.
Department of Food Science, College of Agricultural Sciences,
Pennsylvania State University, University Park 16802.
Microwave heating of infant formula is a common practice despite
concerns of infant scalding. Beyond the issue of physical safety,
little is known about the effects on nutrient content of microwave
heating of infant formula. Casein-predominant infant formula in 120-
and 240-mL glass and plastic nursing bottles of varying colors were
heated for 40 seconds and 60 seconds, respectively. Temperature
profiling was monitored during the heating cycle. Analysis of
riboflavin and vitamin C was made prior to and after heating. Topmost
portions reached a mean temperature of 44.7 +/- 1.7 degrees C and 43.0
+/- 2.4 degrees C for all types of 240-mL and 120-mL bottles,
respectively. Topmost temperatures were significantly hotter than
temperatures reached at other sites. Routine mixing resulted in
formula temperatures which could safely be fed to infants (35.4 +/-
0.3 degrees C and 33.9 +/- 0.2 degrees C for 240-mL and 120-mL
bottles, respectively). There was no significant loss of either
riboflavin or vitamin C. Protocols for microwave heating are given.
PMID: 1518698 [PubMed - indexed for MEDLINE]
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